[dpdk-dev] [PATCH 08/12] net/sfc: introduce descriptor space check in Tx prepare

[Andrew Rybchenko <arybchenko@solarflare.com>]

From: Igor Romanov <igor.romanov@oktetlabs.ru>

Add descriptor space check to Tx prepare function to inform a caller
that a packet that needs more than maximum Tx descriptors of a queue
can not be sent.

Signed-off-by: Igor Romanov <igor.romanov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
---
 drivers/net/sfc/sfc_dp_tx.h   | 31 ++++++++++++++++++++++++++++++-
 drivers/net/sfc/sfc_ef10_tx.c |  4 +++-
 drivers/net/sfc/sfc_tx.c      |  9 ++++++++-
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/drivers/net/sfc/sfc_dp_tx.h b/drivers/net/sfc/sfc_dp_tx.h
index c42d0d01f..ebc941857 100644
--- a/drivers/net/sfc/sfc_dp_tx.h
+++ b/drivers/net/sfc/sfc_dp_tx.h
@@ -196,8 +196,13 @@ const struct sfc_dp_tx *sfc_dp_tx_by_dp_txq(const struct sfc_dp_txq *dp_txq);
 
 static inline int
 sfc_dp_tx_prepare_pkt(struct rte_mbuf *m,
-			   uint32_t tso_tcp_header_offset_limit)
+			   uint32_t tso_tcp_header_offset_limit,
+			   unsigned int max_fill_level,
+			   unsigned int nb_tso_descs,
+			   unsigned int nb_vlan_descs)
 {
+	unsigned int descs_required = m->nb_segs;
+
 #ifdef RTE_LIBRTE_SFC_EFX_DEBUG
 	int ret;
 
@@ -214,11 +219,35 @@ sfc_dp_tx_prepare_pkt(struct rte_mbuf *m,
 
 	if (m->ol_flags & PKT_TX_TCP_SEG) {
 		unsigned int tcph_off = m->l2_len + m->l3_len;
+		unsigned int header_len = tcph_off + m->l4_len;
 
 		if (unlikely(tcph_off > tso_tcp_header_offset_limit))
 			return EINVAL;
+
+		descs_required += nb_tso_descs;
+
+		/*
+		 * Extra descriptor that is required when a packet header
+		 * is separated from remaining content of the first segment.
+		 */
+		if (rte_pktmbuf_data_len(m) > header_len)
+			descs_required++;
 	}
 
+	/*
+	 * The number of VLAN descriptors is added regardless of requested
+	 * VLAN offload since VLAN is sticky and sending packet without VLAN
+	 * insertion may require VLAN descriptor to reset the sticky to 0.
+	 */
+	descs_required += nb_vlan_descs;
+
+	/*
+	 * Max fill level must be sufficient to hold all required descriptors
+	 * to send the packet entirely.
+	 */
+	if (descs_required > max_fill_level)
+		return ENOBUFS;
+
 	return 0;
 }
 
diff --git a/drivers/net/sfc/sfc_ef10_tx.c b/drivers/net/sfc/sfc_ef10_tx.c
index 3d6ba4292..e7ab993dd 100644
--- a/drivers/net/sfc/sfc_ef10_tx.c
+++ b/drivers/net/sfc/sfc_ef10_tx.c
@@ -349,7 +349,9 @@ sfc_ef10_prepare_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 		}
 #endif
 		ret = sfc_dp_tx_prepare_pkt(m,
-				txq->tso_tcp_header_offset_limit);
+				txq->tso_tcp_header_offset_limit,
+				txq->max_fill_level,
+				SFC_EF10_TSO_OPT_DESCS_NUM, 0);
 		if (unlikely(ret != 0)) {
 			rte_errno = ret;
 			break;
diff --git a/drivers/net/sfc/sfc_tx.c b/drivers/net/sfc/sfc_tx.c
index e128bff90..4037802e6 100644
--- a/drivers/net/sfc/sfc_tx.c
+++ b/drivers/net/sfc/sfc_tx.c
@@ -709,8 +709,15 @@ sfc_efx_prepare_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 	for (i = 0; i < nb_pkts; i++) {
 		int ret;
 
+		/*
+		 * EFX Tx datapath may require extra VLAN descriptor if VLAN
+		 * insertion offload is requested regardless the offload
+		 * requested/supported.
+		 */
 		ret = sfc_dp_tx_prepare_pkt(tx_pkts[i],
-				encp->enc_tx_tso_tcp_header_offset_limit);
+				encp->enc_tx_tso_tcp_header_offset_limit,
+				txq->max_fill_level, EFX_TX_FATSOV2_OPT_NDESCS,
+				1);
 		if (unlikely(ret != 0)) {
 			rte_errno = ret;
 			break;
-- 
2.17.1